Method for providing a narrow flange on a large rotor forging



March 7, 1967 L. P. GROBEL ETAL METHOD FOR PROVIDING A NARROW FLANGE ONA LARGE ROTOR FORGING Filed Sept. 16, 1964 F |G.l

INVENTORSI LLOYD P. GROBEL, DURWARD R. DeFOREST, BY 4] W THEIR ATTORNEY.

United States Patent 3,307,252 METHOD FOR PROVIDING A NARROW FLANGE ON ALARGE ROTOR FORGING Lloyd P. Grobel and Durward R. De Forest,Schenectady,

N.Y., assignors to General Electric Company, a corporation of New YorkFiled Sept. 16, 1964, Ser. No. 396,937

3 Claims. (Cl. 29416) This invention relates to an improved method forproviding a relatively narrow flange on a very large cylindrical forgedrotor, such as the kind employed in very.

large rotating equipment used in steam turbine-generator powerplants.More, particularly, this invention relates to an improved method forproviding a narrow flange on a generator rotor when efforts are beingmade to reduce over-all rough forging weight.

The rotor of a steam turbine-generator which carries the filed coils forthe generator is commonly manufactured from a cylindrical forging. Suchforgings are extremely large and heavy, a typical forging being on theorder of 45 feet long and 5 feet in diameter along the body portion, andweighing 160 tons. Due to the nature of the forging process, it isdiflicult to forge a relatively narrow flange. Ordinarily it isnecessary to forge a relatively wide flange, out of which the narrowflange is rough machined. This often involves filling the space betweentwo flanges with solid metal. Obviously, this procedure adds weight tothe forging.

Another method used has been to make the flange by manufacturing aseparate ring and shrinking it onto a reduced diameter rotor portion toform the narrow flange. The difliculty with the latter method ariseswhen there are other flanges or enlarged diameter portions on eitherside, since in this case, the shrunk-on ring cannot be passed over theenlarged diameter portions.

As rotor forgings have reached extremely large diameter and weight,every eflfort is made to design the rough forging in such a way as toreduce the amount of metal. The present invention is concerned with animproved method for providing a narrow flange on the rotor forgingwithout the necessity for adding additional metal to an already largeforging and then having to remove the additional metal during subsequentmachining operations.

Accordingly, one object of the present invention is to provide animproved method for furnishing a relatively narrow flange on a verylarge rotor forging, without hav ing to add rough forging metal and thenremove same.

A more specific object of the invention is to provide an improved methodfor furnishing a fan ring on a large generator rotor.

Other objects and advantages will be apparent from the followingdescription, taken in connection with the accompanying drawing, inwhich:

FIG. 1 is a perspective view of a complete generator rotor forgingduring one stage of manufacture,

FIG. 2 is an enlarged view, taken in cross section, of one end of theforging of FIG. 1 after rough machining, and

FIG. 3 is an enlarged view, taken in cross section, illustrating thegenerator rotor of FIG. 2 at a later stage of manufacture.

Briefly stated, the invention is practiced by providing additional metalon some other convenient rotor portion lying adjacent the desiredlocation of the narrow flange, cutting a hollow ring from one side ofthis rotor portion, moving the ring axially to the new location on therotor, and attaching the ring to the rotor, such as by shrink fit.

Referring to FIG. 1 of the drawing, a perspective view is shown of aforging in an intermediate stage of manufacture. The rotor includes acentral body portion 1 with spindle portions 2. The spindle portionsinclude intermediate diameter sections 2a and small diameter sections2b, the latter being adapted to support the rotor in bearings (notshown). One end of the generator rotor normally terminates in a stub 3,which is coupled to the exciter, .while the other end comprises acoupling flange 4 for attachment to a similar steam turbine shaftcoupling flange (not shown). The body portion 1 may have longitudinalwinding slots machined in the rotor at this stage, but these are omittedin order to avoid obscuring the invention.

In the case of gas-cooled generators, the rotor normally includes fanblades mounted on relatively narrow flanges 5, 6 at opposite ends of therotor called fan rings. Also shown are centering rings 7, 8 which arenot attached to the intermediate spindle portion 2a, but which will belater attached to a retaining ring holding the electrical windings inplace.

Observing the right-hand end of the rotor, it will be seen thatcentering ring 8 can be passed over the extending stub 3 with nodifliculty. Also, fan ring 6 can be placed over stub 3 and attached tointermediate shaft portion 2a with a shrink fit, if desired.

Observing the other end of the rotor, however, it will be seen thatrings 5, 7 will not pass over the integral coupling flange 4. It isundesirable to make the coupling flange out of a separate ring becauseof the torsional stress it will undergo in operation. Although flange 5could be forged in the location shown, considerable unusable metal wouldhave to be added to the rough forging to do this. The weight of thisunusable metal is substantial and may become prohibitive if forgingcapacity is a limiting factor of design.

Referring now to FIG. 2 of the drawing, the section of therough-machined forging shows the body portion 1,

the intermediate shaft spindle portion 2a, the small diameter spindleportion 2b, and the coupling flange 4.

In accordance with the invention, an extra metal portion 4a is addedabove and beyond that which would be required for coupling flange 4. Theaxial length of portion 4a is just suflicient for the fan ring and theparting tool which will later separate it from coupling flange 4.Similarly, the body portion 1 is increased in an axial dimension with anadditional metal portion 1a, to provide sufficient width for a centeringring. The final positions to be occupied by the fan ring and centeringring are shown in phantom lines at 5', 7'.

Referring now to FIG. 3 of the drawing, the fan ring 5 and centeringring 7 are shown in their final positions. The metal which has beenremoved from the coupling flange 4 and body portion 1 is now indicatedby phantom lines at 4a and 1a.

The cutting of the rings 5, 7 is afforded by means of well-knownmachining techniques. Radial and axial parting cuts are made into thecoupling flange as it appears in FIG. 2 in order to separate portion 4a.This is then moved axially where it is shrunk onto the intermediateshaft portion 2a to become the fan ring 5. Additional machiningoperations may then be performed on the fan ring.

Similarly, the ring which is parted from the body portion out of metal1a now becomes a centering ring 7. Although not material to the presentinvention, FIG. 3 shows the fan blades 9 attached to the fan ring andalso shows the retaining ring 10 as it is attached to the centeringring.

Other variations of the invention will become apparent to those skilledin the art. For example, it should be apparent that both the fan ring 5and centering ring 7 could be obtained from the coupling flange ifdesired. However, due to the fact that centering ring 7 is of greaterdiameter, it is most conveniently obtained from the body portion.

providing extra metal on said couplingflange having a widthslightlygreater than the width of said fan ring, and also providing extra metalon the body portion having a width slightly greater than that of saidcentering ring, providing a fan ring by making radial and axial cutsinto said extra metal portion of the coupling flange, providing acentering ring by making radial and axial cuts into said extra metal onthe body portion, moving said fan ring axially to a location separatedfrom the body portion by the centering ring and attaching it to saidrotor spindle portion, whereby the centering ring is disposed betweenthe fan ring and the body portion.

2. The method of providing a relatively narrow flange on a largecylindrical forging having two enlarged diameter portions separated by areduced diameter portion :omprising the steps of:

providing an extra axial length of metal on one of said enlargeddiameter portions having a width slightly greater thanthe desired widthof said flange,

true spirit and scope of removing a ring from said enlarged diameterportion by making radial and axial parting cuts into said extra metalportion,

moving said ring axially to another location between said enlargeddiameter portions, and

attaching said ring to said reduced diameter portion to provide a narrowflange thereon.

3. The method of providing a relatively narrow flange on a cylindricalrotor forging having two enlarged diameter portions separated by areduced diameter portion comprising the steps of:

providing extra metal on one of said enlarged diameter portions having awidth slightly greater than the desired width of said flange,

removing a hollow ring from the first enlarged diameter portion bymaking radial and axial parting cuts into said extra metal portion,

moving said ring axially to a location adjacent an enlarged diameterportion, and

shrinking said ring onto the reduced diameter portion to provide anarrow flange thereon.

References Cited by the Examiner UNITED STATES PATENTS 7/1932 Gundersenet a1. 10-10 1/1951 Brown 29447

1. THE METHOD OF PROVIDING A FAN RING AND A CENTERING RING ON AGENERATOR ROTOR FORGING HAVING A BODY PORTION AND A COUPLING FLANGESPACED BY A REDUCED DIAMETER SPINDLE PORTION, COMPRISING THE STEPS OF:PROVIDING EXTRA METAL ON SAID COUPLING FLANGE HAVING A WIDTH SLIGHTLYGREATER THAN THE WIDTH OF SAID FAN RING, AND ALSO PROVIDING EXTRA METALON THE BODY PORTION HAVING A WIDTH SLIGHTLY GREATER THAN THAT OF SAIDCENTERING RING, PROVIDING A FAN RING BY MAKING RADIAL AND AXIAL CUTSINTO SAID EXTRA METAL PORTION OF THE COUPLING FLANGE, PROVIDING ACENTERING RING BY MAKING RADIAL AND AXIAL CUTS INTO SAID EXTRA METAL ONTHE BODY PORTION, MOVING SAID FAN RING AXIALLY TO A LOCATION SEPARATEDFROM THE BODY PORTION BY THE CENTERING RING AND ATTACHING IT TO SAIDROTOR SPINDLE PORTION, WHEREBY THE CENTERING RING IS DISPOSED BETWEENTHE FAN RING AND THE BODY PORTION.